Apparatus for conditioning the atmosphere in a vacuum chamber

ABSTRACT

In the invention, the atmosphere in a vacuum chamber ( 1 ) is conditioned using a primary pump ( 3 ), a secondary pump ( 2 ), speed control means ( 6, 7 ) for controlling the speed of the primary pump, and at least first gas treatment means ( 5 ) adapted for treating the extracted gases downstream from the primary pump ( 3 ). The vacuum chamber ( 1 ) is contained in a room ( 130 ) having a false floor ( 36 ) covering a space ( 37 ). The primary pump ( 3 ) and the gas treatment means ( 5 ) are housed in the available space ( 37 ) under the false floor ( 36 ), so that the secondary pump ( 2 ) can be placed in the immediate vicinity of the vacuum chamber ( 1 ), and the primary pump ( 3 ) is in the proximity of the vacuum chamber ( 1 ).

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to methods and apparatus for pumping gases out from a vacuum process chamber such as entrance loadlock, exit loadlock, transfer chamber, reaction chamber, and any other vacuum module where the wafers are processed in manufacturing semiconductor electronic components.

[0002] In manufacturing semiconductor electronic components, an important step consists in treating a semiconductor substrate in a controlled atmosphere at very low pressure, e.g. for depositing layers of various materials by plasma deposition.

[0003] In industrial production, substrates, in the form of wafers, are conditioned and brought successively into a process chamber through an airlock or through a transfer chamber. In the vacuum chambers, the atmosphere must be controlled very accurately, in particular to avoid the presence of any impurity or of any pollution.

[0004] Progress made in recent years in the semiconductor industry is essentially related to the increase in the integration of electronic circuits into components of a few square millimeters in area, defined on silicon wafers that are increasingly large.

[0005] Numerous (up to 400) technological steps are required to make such circuits, and, during the process, the pressure in the process chamber is subjected to sudden variations between various steps during which the pressure must be controlled and set to appropriate values.

[0006] Generating the low-pressure controlled-atmosphere in the chamber requires the use of effective pumping systems, generally comprising a primary pump whose outlet is connected to atmosphere and whose inlet is connected to the outlet of a secondary pump such as a turbomolecular pump whose inlet is connected to the chamber.

[0007] The process steps in the process chamber require the presence of special gases, and, by acting on the substrate, they generate gaseous compounds that must be removed. As a result, the pumping system must pump a variable atmosphere containing gaseous compounds that must be treated by gas treatment apparatus in order to deliver to atmosphere only compounds that are inoffensive.

[0008] Currently, pumping and gas treatment systems are situated remote from chambers, i.e. they are connected to chambers via long and costly pipes that are over ten meters long.

[0009] The reason behind that distance and those pipes is that current pumping and gas treatment systems are heavy and voluminous, and they give rise to adverse effects such as vibrations that it is essential to avoid in the process chamber.

[0010] Currently, an electronic component factory is therefore designed in a building having at least two levels, the upper level containing the process chamber(s), and the lower level containing the pumping and gas treatment apparatus. Pipes interconnect the two levels to convey the vacuum.

[0011] The pipes which are essential in known structures suffer from several drawbacks:

[0012] the pipes themselves generate vibrations;

[0013] the pipes constitute a large surface area on which the pumped gases can deposit in the form of particles; particles deposited in that way can backscatter from the pipe into the vacuum chamber, thereby increasing the contamination of the chamber during subsequent steps of the process;

[0014] the pipes require major mechanical support means;

[0015] to reduce the deposits in the pipes, it is possible to provide temperature control, but such control is extremely costly and very difficult to implement;

[0016] a monitoring and control system that is complex to implement must be provided for reasons of safety in the event of leakage, since the pumped gases are harmful;

[0017] the considerable amount of space needed requires large facilities and large floor areas for the factories; their cost is very high; losses from the cold line are non-negligible.

SUMMARY OF THE INVENTION

[0018] An object of the invention is to integrate in the immediate vicinity of the vacuum chamber the various elements making up the vacuum line, thereby eliminating the problems due to the piping. An object is thus to design a system that can be connected directly to the vacuum chamber, thereby making it possible to direct the effluent as quickly as possible to the gas treatment apparatus, thereby improving the effectiveness thereof.

[0019] But a problem is then that the immediate proximity of the active members of the vacuum line constitutes an increased risk of polluting the vacuum chamber, it being possible for the pollution to be, in particular, chemical, thermal, or mechanical.

[0020] For this reason, the invention aims both to reduce the cost of the installations by avoiding the presence of pipes between the process chamber and the pumping and gas treatment apparatus, and also to reduce the risks of polluting the vacuum chamber.

[0021] Another object of the invention is to facilitate adapting the pumping system to various vacuum chamber structures, by optimizing the effectiveness of the process control in the vacuum chamber.

[0022] Another object of the invention is to improve the effectiveness of the gas treatment in order to eradicate or to reduce appropriately any discharge to the atmosphere of toxic matter.

[0023] A problem resulting from the immediate proximity of the active members of the vacuum line relative to the process chamber is that the active members risk occupying a significant amount of room around the process chamber, thus preventing users from circulating around the process chamber, and also preventing other appliances that might be necessary from being put into place.

[0024] Another object of the invention is thus to leave the circulation space around the process chambers free, by preventing the active members of the vacuum line from occupying said circulation space.

[0025] Another object of the invention is to make it possible to dispose the pumping means in the immediate vicinity of the process chamber, in particular by reducing the size of said means.

[0026] To achieve these objects and others, the invention provides apparatus for conditioning the atmosphere in a vacuum chamber, said apparatus comprising:

[0027] a pumping line comprising a primary pump and at least one upstream secondary pump;

[0028] downstream from the primary pump, gas treatment means for treating the extracted gases;

[0029] wherein

[0030] the vacuum chamber is contained in a room having a false floor covering a space;

[0031] the primary pump is housed in the available space under the false floor, in the proximity of the vacuum chamber.

[0032] The gas treatment means may advantageously be housed in the available space under the false floor.

[0033] In a first alternative, the false floor comprises removable floor tiles covering the primary pump, the gas treatment means, and the gas analyzer means.

[0034] In a second alternative, the top portion of the primary pump and the top portion of the gas treatment means themselves constitute surface portions of the false floor.

[0035] A support plate can advantageously be disposed in the floor beneath the primary pump and the gas treatment means.

[0036] In an advantageous embodiment, making it possible for the operation of the process chamber to be further improved, the primary pump and the gas treatment means are enclosed together in an isolation enclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other objects, characteristics, and advantages of the present invention appear from the following description of particular embodiments given with reference to the accompanying drawings, in which:

[0038]FIG. 1 is a structural diagrammatic view of an embodiment of pumping and gas treatment apparatus of the present invention;

[0039]FIG. 2 is a timing diagram showing the pressure variation before, during, and after a treatment step in a process chamber;

[0040]FIG. 3 is a three-dimensional diagram showing a transfer function for a pumped gas, giving the relationship between pumping speed, pumping flow rate, and the pressure obtained in the process chamber; and

[0041]FIG. 4 is a structural diagrammatic view of apparatus according to an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] In the embodiment shown in FIG. 1, the system of the invention makes it possible to control mainly the pressure inside a vacuum chamber 1, by pumping by means of a pumping line essentially comprising a secondary pump 2 having an inlet connected to the vacuum chamber 1 and an outlet connected to the primary pump 3 which itself has an outlet connected to atmosphere via an outlet pipe 4 via a gas treatment system 5.

[0043] The primary pump 3 is a variable-speed dry primary pump suitable for delivering at atmospheric pressure. The secondary pump 2 is, for example, a turbomolecular pump suitable for establishing the appropriate low pressure in the vacuum chamber 1, and for delivering at the inlet pressure of the primary pump 3 via a pipe 30.

[0044] Control means are provided for controlling the speed of the primary pump 3, e.g. a controller 6 connected to the primary pump 3 via a primary pump control line 7. In a manner known per se, the primary pump 3 includes power supply apparatus suitable for achieving the speed which is variable as a function of the signals received over the primary pump control line 7.

[0045] Similarly, control means may be provided for controlling the speed of the secondary pump 2, such as, for example, the same controller 6 connected to the secondary pump 2 via a secondary pump control line 8.

[0046] First gas analyzer means 9 are suitable for analyzing the gases extracted upstream from the primary pump 3, and for producing first analysis signals which are sent to the controller 6 via a first analysis signal line 10. The controller 6 is programmed such as to constitute first signal processing means for producing a speed control signal as a function of the first analysis signals procured by the first gas analyzer means 9, and for transmitting said speed control signal to the power supply apparatus of the primary pump 3 via the primary pump control line 7.

[0047] For this purpose, the controller 6 includes a memory in which a transfer function is recorded, which transfer function makes it possible to compute the speed of the primary pump 3 for producing the appropriate pressure conditions in the vacuum chamber 1. Thus, the processing means installed in the controller 6 perform relationship matching between the first analysis signals that reach them at their first input 100 via the first analysis signal line 10 and the speed control signal at their output 70 connected to the primary pump 3 via the primary pump control line 7, using a pre-recorded transfer function that represents, for each gas mixture present in the vacuum chamber during a step of the process, the relationship between the pumping speed, the flow rate of the gas mixture, and the resulting pressure in the vacuum chamber 1.

[0048] By means of the gas analysis system integrated into the vacuum generation system, as shown in FIG. 1, it becomes possible to connect the secondary pump 2 to the vacuum chamber 1 via a pipe 21 that is of short length, generally less than 3 meters. In practice, it becomes possible to place the secondary pump 2 in a position adjacent to the vacuum chamber 1, from which it is optionally separated by the pipe 21 provided with an isolation valve 11.

[0049] In a variant, the pipe 21 may be no more than the isolation valve 11.

[0050] The transfer function implemented in the controller 6 is, by way of example, shown in FIG. 3, for a specific gas mixture. In this figure, it is possible to see the shape of a surface showing the relationship, in a three-dimensional system, between the gas flow rate present in the chamber and plotted along the F axis, the resulting pressure plotted along the P axis, and the pumping speed plotted up the V axis.

[0051] The first function performed by the controller 6 is to adjust the pumping speed in a manner such as to maintain the pressure at a value suitable for each process step in the vacuum chamber 1.

[0052] In addition, the controller 6 uses the analysis of the extracted gases, as procured by the first gas analyzer means 9, the result of the analysis being used to adjust the pumping speed, as a function of the pumped gases, to determine the variation of the pressure in the vacuum chamber 1 during the transient stages of the process.

[0053] In order to adjust the pumping speed as a function of the pumped gases, the transfer function pre-recorded in the controller 6 is thus used. For each gas mixture present in the vacuum chamber 1 during the process, the transfer function represents the relationship between the pumping speed V, the flow rate F and the resulting pressure P in the vacuum chamber 1.

[0054] In the embodiment shown in FIG. 1, the extracted-gas treatment means 5 connected to the primary pump 3 via a pipe 31 are situated downstream from the primary pump 3. At the outlet of the primary pump 3, before the gas treatment means 5, second gas analyzer means 12 are provided that make it possible to determine the nature and the state of the pumped gases, and that produce second analysis signals which are sent via a line 13 to second signal processing means installed in the controller 6. The second signal processing means, in the controller 6, are suitable for producing second control signals as a function of the analysis signals received from the second gas analyzer means 12, which second control signals can be sent to the speed control apparatus for controlling the speed of the primary pump 3 via the primary pump control line 7.

[0055] By means of the information given by the second gas analyzer means 12, the controller 6 is informed of the nature and the state of the pumped gases, and adapts the pumping parameters to optimize the treatment performed by the gas treatment apparatus 5. For this purpose, the primary pump 3 is associated with pump temperature control apparatus 14, and with a dilution gas injector 15 connected to the gas treatment apparatus 5 via a pipe 20. The dilution gas injector 15 makes it possible, if necessary and in controlled manner, to inject dilution gases into the primary pump 3, making it possible to dilute the pumped gases and to prevent them from condensing in the primary pump 3. The dilution gas injector 15 and the pump temperature control apparatus 14 are controlled by the controller 6 which can thus adapt the pumping parameters such as the temperature of the body of the primary pump 3 and the injection of dilution gas, in addition to the speed of the primary pump 3. These possibilities enable the effectiveness of the gas treatment means 5 to be improved significantly so as to reduce the presence of toxic elements at the outlet 4 to as low as possible.

[0056] Thus, the apparatus includes pumping conditioning means including pump temperature control apparatus 14 associated with said primary pump 3, and apparatus 15 for injecting dilution gas into said primary pump 3 and receiving said second control signals to control them so as to optimize the effectiveness of the gas treatment means 5.

[0057] In the embodiment shown in FIG. 1, third gas analyzer means 16 are provided, mounted on the pipe 4 and adapted for analyzing the gases output by the gas treatment means 5 and for adapting the gas treatment means 5 themselves as a function of the result of said analysis. In practice, the third gas analyzer means 16 produce signals sent to the controller 6 via the transmission line 22, and the controller 6 controls the gas treatment means 5 via a gas treatment control line 17. Thus, the gases exiting from treatment are analyzed so as to adapt the treatment itself as a function of the result of said analysis. For example, the pumping can be interrupted in the event that a treatment defect is detected by the third gas analyzer means 16.

[0058] The gas analyzer means 9, 12, and 16 can, a priori, be of any known type making it possible to analyze rapidly the gases in the short pipes 30, 31, and 4 respectively between the secondary pump 2 and the primary pump 3, between the primary pump 3 and the gas treatment apparatus 5, and at the outlet of the gas treatment apparatus 5.

[0059] In an embodiment, such gas analyzer means 9, 12, or 16 may include apparatus for ionizing the gases to be analyzed, which apparatus is constituted by at least one plasma source dedicated to analysis and put in contact with the gases in the pipe, and generating plasma from the gases to be analyzed. The plasma source is fed by a generator suited to the chosen type of plasma source. For example, the plasma source may be a microwave source of the resonant cavity type or of the type using the principle of surface wave propagation, and the generator is a microwave generator. In another embodiment, the plasma source is a radiofrequency plasma source of the inductive coupling plasma (ICP) type, and the generator is a radiofrequency (RF) generator.

[0060] The ionized gases may be analyzed by ionized gas analysis apparatus of the optical spectrometer type having a probe situated in the vicinity of the dedicated plasma source, analyzing the variation of a radiative spectrum emitted by the generated plasma. The radiation emitted by the atoms, molecules, and ions excited by the free electrons of the plasma are transmitted to the optical emission spectrometer which analyzes the variations in the radiations and deduces therefrom information relating to the components of the ionized gases.

[0061] The gas analyzer means 9, 12, or 16 may be integrated in series in the pipe 30, 31, or 4 whose gaseous effluent is to be controlled, or else it may be mounted on said pipe via an external fitting.

[0062] It can be understood that the controller 6 may be implemented in known manner, based on a microprocessor associated with memories and input-output circuits. A suitable program and data are recorded in the memory of the controller 6 so as to control the members of the vacuum generation and vacuum control apparatus. It is possible to enter in the memory in particular the data of the transfer function as shown in FIG. 3, which data is pre-computed as a function, in particular, of the geometrical shape of the vacuum chamber 1, and of the various vacuum-generating members.

[0063] In accordance with the invention, it is advantageously possible to provide a prior training step in which the pumping speed is caused to vary in the presence of at least some of the gas mixtures that can be present during the process steps in the vacuum chamber 1, and the flow rate and the resulting pressure in the vacuum chamber 1 are measured to determine the transfer function. By means of this training step, the apparatus of the invention can be self-adaptive to the vacuum chamber 1. For this purpose, a pressure sensor 18 is provided, which pressure sensor is disposed in the vacuum chamber 1, and connected via a pressure line 19 to the controller 6. A training program is recorded in the memory of the controller 6 so as to cause the variations in the speed of the primary pump 3 and/or of the secondary pump 2 in the presence of the appropriate gas mixtures in the vacuum chamber 1.

[0064]FIG. 2 shows the conditions under which the pumping apparatus of the invention can operate when used to control the atmosphere in a vacuum chamber 1. The figure shows a known example of a timing diagram showing how the pressure varies over time and obtained with prior art pumping apparatus. During a first period 120, a substrate is transferred into a process chamber 1. During a second period 121, the pressure is lower, and the substrate is then treated in the process chamber 1. This treatment step may correspond to various treatment gases being present. During a third period 122, the pressure is higher, and the substrate is removed from the process chamber 1. In that known timing diagram, it can be observed that pressure fluctuations can be observed, in particular in the vicinities of the transient stages of the treatment. Those pressure fluctuations induce turbulence and risks of pollution in the process chamber 1. The invention makes it possible to reduce very significantly or even to eradicate the pressure fluctuations and the resulting risks of pollution.

[0065] The apparatus of the invention may, as shown in FIG. 1, include the primary pump 3 connected to a single secondary pump 2 for pumping the gases from the vacuum chamber 1.

[0066] Alternatively and advantageously, it is possible for the primary pump 3, together with the gas treatment apparatus 5, to be connected to a plurality of secondary pumps 2, each of which is dedicated to a distinct vacuum chamber 1.

[0067] By suitably programming the controller 6 which controls the speed of the primary pump 3 and optionally the speed of the secondary pump 2, as well as the pumping parameters such as the temperature of the body of the primary pump 3 and the injection of dilution gas by means of the apparatus 14 and 15, the invention makes it possible to avoid deposits and turbulence in the vacuum chamber 1, and to avoid deposits in the pumping line. The pumping function and the gas treatment function are thus better integrated, which makes it possible to reduce very significantly the costs of the semiconductor manufacturing installations, to increase production capacity, and to improve flexibility significantly by making it easier to dispose the elements of the semiconductor production unit geographically. At the same time, the control of the vacuum function and of the process in the vacuum chamber is improved significantly, and the treatment of the pumped gases is improved.

[0068]FIG. 1 shows an advantageous embodiment of the present invention, which embodiment includes isolation means enabling the disturbance caused by the pumping apparatus to the vacuum chamber 1 to be further reduced.

[0069] For this purpose, the primary pump 3, the gas treatment means 5, and the gas analyzer means 9, 12, and 16 are enclosed together in an isolation enclosure 23. The isolation enclosure 23 is a sealed enclosure that forms a mechanically-rigid assembly.

[0070] Preferably, and as shown in FIG. 1, the isolation enclosure 23 is provided with temperature monitoring and regulation apparatus 24 making it possible to monitor and to regulate the temperature of the contents of the isolation enclosure 23 so as to avoid transmitting thermal disturbance to the elements outside the isolation enclosure 23, in particular to the vacuum chamber 1.

[0071] Also preferably, the isolation enclosure 23 is provided with active vibration-compensating means 25 making it possible to compensate actively the mechanical vibrations generated by the contents of the isolation enclosure 23, in particular by the primary pump 3.

[0072] The active vibration-compensating means 25 comprise vibration sensors associated mechanically with the isolation enclosure 23, and vibration generators controlled so as to produce vibrations in phase opposition with the vibrations produced by the contents of the isolation enclosure 23.

[0073] It is thus possible to reduce the mechanical, thermal, and chemical disturbance generated by the vacuum generation apparatus which can thus be disposed in the immediate vicinity of the vacuum chamber 1.

[0074] Preferably, and as shown in FIG. 1, the isolation enclosure 23 further encloses a controller 6 which forms the signal processing means for generating the speed control signal for controlling the speed of the primary pump 3 and/or the speed of the secondary pump as a function of the signals that it receives from the gas analyzer means 9 and 12.

[0075] It can be understood that each of the various above-described isolation means could be adapted to a vacuum line independently of the presence or of the absence of the gas analyzer means and of the other means of the invention for controlling the speed of the pumps and the other active members as a function of the gas analysis.

[0076] In accordance with the invention, the controller 6 may advantageously be programmed to control the active members of the apparatus (pumps, pumping parameters) in a different manner that is adapted and appropriate as a function of the status of the vacuum chamber equipment 1: production stage; test stage; maintenance stage; standby stage.

[0077]FIG. 4 shows advantageous features of the present invention, enabling the floor area required by a vacuum line and by its components in the proximity of the vacuum chamber 1 to be reduced, leaving the space around the vacuum chamber free to enable operators to intervene on this chamber without being hindered by the vacuum generator and gas treatment components.

[0078] In this FIG. 4, the vacuum chamber is contained in a room 130, e.g. a clean room, having a false floor 36 covering a space 37. The primary pump 3 and the gas treatment means 5, and possibly the gas analyzer means 9, 12, 16, are housed in the available space 37 under the false floor 36 in the proximity of the vacuum chamber 1. These components are fixed under the floor tiles of the false floor 36 at fixings which support the floor tiles.

[0079] The false floor 36 can advantageously comprise removable floor tiles 32 enabling maintenance or repair intervention on the active elements of the vacuum line. In a first possibility, the removable floor tiles 32 can merely cover the primary pump 3, the gas treatment means 5, and possibly the gas analyzer means 9, 12, 16.

[0080] Alternatively, as shown in FIG. 4, the top portion 33 of the primary pump 3 and the top portion 34 of the gas treatment means 5 themselves constitute surface portions of the false floor 36.

[0081] For effectiveness purposes, a support plate 35 is preferably in the floor beneath the primary pump 3 and the gas treatment means 5, between the fixing pillars of the false floor 36.

[0082] The present invention is not limited to the embodiments which are explicitly described, but rather it includes the various variants and generalizations that are accessible to the person skilled in the art. 

1. Apparatus for conditioning the atmosphere in a vacuum chamber, said apparatus comprising: a pumping line comprising a primary pump and at least one upstream secondary pump; downstream from the primary pump, gas treatment means for treating the extracted gases; wherein : the vacuum chamber is contained in a room having a false floor covering a space; the primary pump is housed in the available space under the false floor, in the proximity of the vacuum chamber.
 2. Apparatus according to claim 1, wherein the gas treatment means are housed in the available space under the false floor.
 3. Apparatus according to claim 2, wherein the false floor comprises removable floor tiles covering the primary pump and the gas treatment means.
 4. Apparatus according to claim 2, wherein the top portion of the primary pump and the top portion of the gas treatment means themselves constitute surface portions of the false floor.
 5. Apparatus according to claim 2, wherein a support plate is disposed in the floor beneath the primary pump and the gas treatment means.
 6. Apparatus according to claim 5, wherein the support plate is between fixing pillars of the false floor.
 7. Apparatus according to claim 1, wherein the secondary pump is connected to the vacuum chamber via a pipe of length generally less than 3 meters.
 8. Apparatus according to claim 7, wherein the secondary pump is adjacent to the vacuum chamber.
 9. Apparatus according to claim 2, wherein the primary pump and the gas treatment means are enclosed together in an isolation enclosure.
 10. Apparatus according to claim 9, wherein the isolation enclosure is provided with temperature monitoring and regulation apparatus for monitoring and regulating the temperature of the contents of the isolation enclosure.
 11. Apparatus according to claim 9, wherein the isolation enclosure is provided with active vibration-compensating means for compensating the mechanical vibrations generated by the contents of the isolation enclosure.
 12. Apparatus according to claim 9, wherein the isolation enclosure further encloses a controller for controlling the speed of the primary pump and/or the speed of the secondary pump.
 13. Apparatus according to claim 12, wherein the controller is programmed to control the active members of the apparatus (pumps, pumping parameters) in different manners that are adapted and appropriate as a function of the status of the vacuum chamber equipment: production stage; test stage; maintenance stage; standby stage. 